Spinal fusion is a medical procedure by which two or more vertebrae (bones in the spine) are linked together. It is used for a wide range of spinal injuries and has a high success rate. The spine consists of 33 vertebrae, 24 of which are separate. To fuse any of these vertebrae together, a number of different techniques can be used. All rely on the same underlying principle, however.
To initiate spinal fusion, an incision is made where the vertebrae to be fused are located. In the case of vertebrae in the neck, this cut is usually made from the front. In the case of vertebrae in the mid- and lower back, the cut is made in the back. A small bit of bone is then placed between the vertebrae. The vertebrae will then graft themselves to this bone over time, eventually forming one solid structure. Aids such as screws or metal plates may or may not be used in spinal fusion, and will usually only be called upon if it appears that the vertebrae need a splint to hold them in place while the bone grafts.
Some of the reasons for performing spinal fusion surgery are: chronic pain from vertebrae motion, disc problems, spinal deformities and broken vertebrae. Occasionally a small fracture occurs in a vertebra, which allows the bone to move out of its usual position and to grate against another vertebra. This is an extremely painful condition, known as spondylolisthesis, and spinal fusion is a relatively easy way to stop the pain.
Between the vertebrae is tissue known as discs. This tissue may occasionally herniate, pushing out from where it is supposed to be. In this case, the disc most often needs to be removed entirely, leaving a void between the two vertebrae. A small piece of bone is placed where the disc once was, and the two vertebrae fuse together.
In cases where the spine has developed an irregularity, such as the fairly common s-shape known as scoliosis, spinal fusion may be recommended to help return the spine to its proper shape. Since scoliosis is not terribly harmful, spinal fusion is usually only used in cases in which the bending has become very large, or seems to be worsening at a rapid rate.
Lastly, broken vertebrae most often require some amount of spinal fusion as part of the healing process. This is especially the case when the spinal cord itself has been damaged in some way. A fracture does not always require spinal fusion to heal properly, but in cases where it seems the break might be unstable or become unstable over time, fusion will most likely be recommended as a way to safeguard against future injuries.